Mash temp blunder

[Coo brewing]

So I've been AG brewing for about 3 years didn't really start to take things seriously until about 4 months ago after a youtube binge and have always had problems keeping and getting correct mash temps I've got I brew app and that helps with sparge temp calculations but going of the probe I've got built in the keg looks ok .recently bought a hand held thermometer and used it today doing a decoction . Man the in built thermo was reading 68 hand held said 58 so I've been down 10 degree every mash I've done ,beer comes out drinkable but sometimes has no body to it , so now I've got new thermometer every brew should get better from now ,also on my decoction I tried to bring it to mash out from 68-78 I took out 5 litres of grist and about 2litres of liquid boiled it but. Didn't change mash temp at all y
Any body else getting bad temps looks like I might have to get a cooler

 

[MHB]

There is only one way a 7ish Kg decoction wont change the temperature of the main mash - that is if the main mash is at the boiling point!

If there is a serious question lurking in the post you will need to supply a bit more information, just the basic stuff like batch size, L:G at the time you took the decoct portion and WTF you mean by a "hand held thermometer" and why you are confidant that it is accurate - you must be aware by now that not all thermometers are.

Personally I'm very suspicious of brewing software, not wether or not it works but as to how well it is used. It is really important to understand what is going on if you want to brew you should be able to do the calculations, just like a kid at school you don't get a calculator first, you learn how to do maths the hard way when you understand the process you can use a calculator to take out the drudgery. I mean 15 into 23 goes 1 and 8 left over, 15 into 80 goes... gets pretty boring pretty fast but you really do need to understand before just pushing buttons and trust the answer.

Take the decoction equation (good walk through at Braukaiser)
decoction volume = total mash volume * (target temp - start temp) / (boil temp - start temp)
Plug in the information you have for the conditions of your brew, there is no way that a decoction cant raise the temperature of the main mash so you are clearly not measuring something right.
Get the basics right
Mark

 

[Bribie G]

As this is a temperature problem I'd advise you to buy a couple of probe style digital thermometers.
Flame suit on but I've only ever used cheap kitchen shop or Kmart ones.
They do a good job but need to be calibrated.
Calibrate 2 in ice then boiling water. You'll probably find that they are half a degree out so you can take that into account.
Someone will now post that it's impossible to calibrate at mash temperature but in practice I've found that if the thermos closely agree at freezing and boiling then also agree at mash temps then I'm pretty much on the money.
I use them for my yogurt making as well which is very temperature sensitive and get perfect results.
Worst thermometer I ever had was a glass one from a LHBS that proved to be 6 degrees out.

 

[MHB]

I always suggest people get one thermometer they can trust and use that to benchmark any others you use.
And yes Bribie I have had crap thermometers delivered - and promptly returned them (in one case binned in disgust). A good laboratory thermometer that you can trust will set you back $15 or so, a pretty small investment in the scheme of all things brewing.
Mark

 

[manticle]

Other thing is that probe/dial therms only measure one spot. Constantly recirc-ing mashes will be more consistent but mashes have hot and cool spots so check with a good immersion stick thermometer that you trust.

 

[MHB]

Even then you need to be a bit cautious, in a well made mashtun when you are ramping there can be a big difference between the top and the bottom of the grain bed, on the small commercial system I am brewing on it can get up to 10oC if you don't watch the differential between the temperature of the HLT water and the wort coming out the bottom of the grain bed.
Sorting out the issues above picked up about 10% efficacy, the return wort was so hot it was killing off enzymes, a bit of rearranging sensor location made a big difference to the outcome.
Mark

 

[Coo brewing]

Hi guys hi guys thanks for the posts I'm using a converted keg on gas burner it's quite tall and skinny compared to normal 50 litre keg wrapped in some insulation I was only using 4.5 kg of wheat for a 18 litre batch I got all my numbers but just missing on the temp .hand held thermometer was bought from a kitchen shop can't remember the price but was probably the cheapest one there I have recently started reculating (last two batches ) and found that to loose a lot of temp inn the process . Thinking of putting a tap in the mash tun lid so I don't leave the lid ajar with the hose going in , math is really not my strong point so brew soft wear really helped me design my beers and all calculations next time will get temp of grains and adjust to that